The present invention relates to a microwave gas laser oscillating apparatus for providing microwave discharge excitation.
There is a recent tendency to miniaturize gas laser oscillating apparatuses, and to do this, attempts are made to increase the excitation frequency. Conventional power supplies for gas laser oscillators use DC and a high frequency between several 100 kHz and several 10 MHZ but have problems in costs and controllability.
Various microwave excitation gas laser oscillators are now examined, and an example is explained with reference to FIG. 12. This figure shows a configuration of a microwave power supply apparatus for a conventional microwave excitation laser oscillating apparatus.
In FIG. 12, reference numeral 3 is a heater transformer in a heater circuit 1 for applying a heater voltage to a heater section of a magnetron 2 that generates microwaves; 4 is a high-voltage generating circuit for applying a high voltage to a cathode and an anode of the magnetron 2 and to which a high voltage is applied from a switching circuit 5 via a step-up transformer 6 and a high-voltage rectifying circuit 7.
In a microwave power supply apparatus of this configuration, the switching circuit 5 applies about 20 kHz of switching operation to an input DC voltage, which is then applied to the step-up transformer 6. The step-up transformer 6 has its voltage increased up to a value required for oscillate the magnetron 2, rectified by the high-voltage rectifying circuit 7, and then applied to the cathode and anode of the magnetron 2. The heater transformer 3 reduces a commercial 200 VAC or 100 VAC and directly applies it to the heater section of the magnetron 2.
In this configuration, the variation of the commercial voltage is directly reflected in the variation of the heater voltage, but the output from the magnetron 2 does not vary if the heater voltage is within a specified variation range. In addition, the specified value of the variation of the heater voltage is within the variation range of the commercial voltage, and no effect appears in the output from the magnetron 2.
However, no microwave power supply apparatuses of the conventional configuration have means for detecting abnormal oscillation caused by the degradation of the magnetron 2, so the decrease in laser optical output during the abnormal oscillation of the magnetron 2 is a problem. In addition, the magnetron 2 may be degraded in a short time, resulting in short maintenance cycles.
It is thus an object of this invention to prevent abnormal oscillation of the magnetron and to detect degradation of the magnetron in order to increase its service life.
To achieve this object, the present invention comprises a discharge tube that excites a gas by means of discharge to generate a laser light, a magnetron that supplies microwaves to the discharge tube, and a microwave power supply apparatus for supplying power to the magnetron, wherein the microwave power supply apparatus has a heater circuit for applying heater voltage to the heater of the magnetron, and a high-voltage generating circuit for applying a high voltage between the anode and cathode of the magnetron, and wherein the heater circuit controls the heater voltage output to the magnetron from the heater circuit depending on whether the magnetron is stopped from oscillating or is providing a continuous output or an intermittent output.
According to this configuration, the heater temperature varies to a small extent and the heater voltage is controlled at a lower limit value at which the magnetron can oscillate stably, so that the magnetron can oscillate stably and its service life can be increased.
In another embodiment, the invention comprises a discharge tube that excites a gas by means of discharge to generate a laser light, a magnetron that supplies microwaves to the discharge tube, and a microwave power supply apparatus for supplying power to the magnetron, wherein the microwave power supply apparatus comprises a heater circuit for applying heater voltage to the heater of the magnetron, a high-voltage generating circuit for applying a high voltage between the anode and cathode of the magnetron, and an abnormal-voltage detecting circuit for detecting abnormal oscillation of the magnetron through an abnormal voltage generated in an abnormal-voltage-detecting winding provided in a step-up transformer constituting the high-voltage generating circuit.
According this configuration, abnormal voltage generated during abnormal oscillation is detected through the winding of the step-up transformer in order to detect the abnormal oscillation of the magnetron by means of the abnormal-voltage detecting circuit.
In another embodiment, the invention comprises a discharge tube that excites a gas by means of discharge to generate a laser light, a magnetron that supplies microwaves to the discharge tube, and a microwave power supply apparatus for supplying power to the magnetron, wherein the microwave power supply apparatus comprises a heater circuit for applying heater voltage to the heater of the magnetron, a high-voltage generating circuit for applying a high voltage between the anode and cathode of the magnetron, and an abnormal-voltage detecting circuit for detecting a defect in the heater section of the magnetron by detecting an abnormal voltage through a heater-voltage-detecting monitor winding provided in a heater transformer constituting the heater circuit.
This configuration allows it to accurately detect a defect in the heater circuit of the magnetron by detecting a decrease in the heater voltage of the magnetron caused by the lack of the oscillation of the magnetron caused by a short or an open circuit in the heater of the magnetron.
In another embodiment, the invention comprises a discharge tube that excites a gas by means of discharge to generate a laser light, a magnetron that supplies microwaves to the discharge tube, and a microwave power supply apparatus for supplying power to the magnetron, wherein the microwave power supply apparatus comprises a heater circuit for applying heater voltage to the heater of the magnetron, a high-voltage generating circuit for applying high voltage between the anode and cathode of the magnetron, a current detecting element that detects current flowing between the anode and cathode of the magnetron, and an abnormal-current detecting circuit which operates, when detecting that the current value of the current detecting element is abnormal, to stop the operation of only the abnormal microwave power supply.
According to this configuration, the current detecting element detects the current flowing between the anode and the cathode in order that the abnormal-current detecting circuit can stop the operation of the abnormal microwave power supply.
In another embodiment, the invention comprises a discharge tube that excites a gas by means of discharge to generate a laser light, a magnetron that supplies microwaves to the discharge tube, and a microwave power supply apparatus for supplying power to the magnetron, wherein the microwave power supply apparatus comprises a heater circuit for applying a heater voltage to the heater of the magnetron, a high-voltage generating circuit for applying a high voltage between the anode and cathode of the magnetron, abnormal-oscillation detecting means for detecting the abnormal oscillation of the magnetron, and a heater voltage instructing circuit which operates, when the abnormal-oscillation detecting means detects abnormal oscillation of the magnetron, to gradually increase the heater voltage, to store in the heater circuit a heater voltage at which the abnormal oscillation stops, and to output an instruction signal for operation at that heater voltage.
According to this configuration, when abnormal oscillation occurs, the abnormal oscillation is stopped in a short time by increasing the heater voltage and at this heater voltage at which the oscillation is stopped, operation is carried out, so that stable oscillation can be secured even though the magnetron degrades.